1. Field of the Invention
The invention pertains to medical devices for fluids, more particularly syringes with a retractable needle which cannot be reused after an injection has been made.
2. Background of the Prior Art
They syringe art has advanced rapidly in recent years because of the threat of AIDS and other infectious diseases and the inevitability of accidental needle sticks suffered by healthcare providers from the use of needles on infected patients. Used syringes with extended needles present a risk to medical personnel, sanitation employees and others in the disposal chain. The prior art has disclosed a large number of syringes and other medical devices with retractable needles, usually retracting into the barrel or into a needle receiving chamber within the syringe barrel. The most advanced of the retracting syringes are disclosed in our U.S. Pat. Nos. 5,385,551; 5,578,011; 5,632,733; 6,015,438; and 6,090,077, which are all hereby incorporated herein by reference. The syringes disclosed in the foregoing patents are retracted automatically by continued pushing on the plunger handle while an injection is being finished and offer one handed handling and retraction of the syringe so that the healthcare worker never needs to be exposed to a contaminated needle. Plunger actuated automatic retraction of these devices takes place before the needle is removed from the patient. These retractable syringes are suitable for mass production at low cost with a high degree of reliability and repeatability of operation. They are suited to automated production of parts and automated assembly in a number of different barrel sizes, needle sizes and for different uses.
While the syringes described above and other retractable syringes have eliminated or substantially reduced the needle stick problem, some have expressed a need for syringes of one-use which cannot be reused under any circumstances. Most, if not all, retractable syringes require the user to take some action to initiate retraction of the needle after an injection has been made. This leaves the retractable syringe open for a possible reuse if the user fails to retract the needle after one use. A solution to this problem has been proposed in the case of nonretractable syringes by means of various devices which mechanically lock the plunger handle after the first use of the syringe, but none of these devices have a retractable needle. Therefore, the needle remains exposed with the continued potential for needle sticks even though the syringe cannot be reused because the plunger cannot be withdrawn a second time. Examples of syringes with locking plunger handles but which do not retract, include Free et al., U.S. Pat. No. 5,000,737, entitled xe2x80x9cSingle Use Disposable Syringexe2x80x9d; Allison et al., U.S. Pat. No. 5,205,825, entitled xe2x80x9cInsertable Element for Preventing Reuse of Plastic Syringesxe2x80x9d; Kosinski, U.S. Pat. No. 4,973,310, entitled xe2x80x9cSingle-Use Syringexe2x80x9d; Kosinski, U.S. Pat. No. 4,961,728, entitled xe2x80x9cSingle-Use Syringe having Misuse Resistant Featuresxe2x80x9d; Shonfeld et al., U.S. Pat. No. 5,531,691, entitled xe2x80x9cSingle Use Syringe Assemblyxe2x80x9d; and Shonfeld et al., U.S. Pat. No. 5,562,623, entitled xe2x80x9cSingle-Use Syringe Assembly including Spring Clip Lock and Plungerxe2x80x9d. The disclosure of these patents is incorporated herein by reference.
The single-use syringes mentioned above cannot be reused after one injection is made, but a contaminated needle is still extended and must be capped, removed or otherwise disposed of before the syringe is rendered safe. Thus, there is a need for an improved syringe of one-use with a needle that retracts into the syringe barrel after use and which cannot be reused whether or not the needle is retracted.
The present invention is a retracting syringe of one use having a handle operated needle retention chamber which cannot be removed from the syringe barrel. The retracting feature obviates the danger associated with an exposed needle after an injection is made. The positive locking structure assures that the syringe is truly a syringe of one use and cannot be reused. In the various embodiments the movable parts comprising the handle portion and the needle retention chamber are limited in rearward movement and contained in the syringe barrel after one rearward movement of the handle to fill the syringe with fluid and one forward movement of the handle to discharge the fluid from the syringe. The invention serves to eliminate the risk that a retractable syringe, which is supposed to be retracted after one use, could possibly be reused because the operator chose to or failed to activate the retraction mechanism thereby leaving the needle exposed for a second use. This cannot occur because the positive locking structure prevents removal of the needle retention chamber by blocking its removal. The needle retention chamber is retained in the barrel whether or not the retraction mechanism is activated and whether or not the needle is retracted. This suggests that the advantage of the invention can also be applied to a nonretracting syringe where the needle is fixed in the front end of the barrel and this should be considered another aspect of the invention disclosed herein. In a nonretracting syringe, the invention works in the same way to limit or prevent withdrawal of the handle (plunger) from the barrel. If the handle cannot be drawn back a second time, the syringe cannot be refilled with fluid.
An elongated hollow syringe barrel having a front end and an open back preferably has a retractable needle retractably mounted in a retraction structure located in the front end of the syringe barrel and biased for retraction in a rearward axial direction. Movable parts comprising a handle attached to a needle retention chamber performs the function of an ordinary syringe plunger in the barrel. The front end portion of the needle retention chamber has a piston mounted in sliding sealed contact with the interior of the barrel. The movable parts are moved by means of the handle extending from the open back of the barrel. The back end portion of the handle portion has a cap for applying thumb force to the handle. The needle retention chamber has an openable sealed opening in front to receive the retracted needle into the needle retention chamber when the retraction mechanism is actuated by forward movement of the plunger after the fluid has been discharged during an injection into a patient. Retraction of the needle into the needle retention chamber is triggered by forward movement of the needle retention chamber against the retraction structure in response to movement of the handle after the injection is completed.
Positive locking structure is located within the syringe barrel to limit movement of the needle retention chamber in a rearward direction and prevent its removal from the syringe barrel after one use. The positive locking structure is adapted to have no effect on one rearward movement and one forward movement of the movable parts to the fullest extent of forward movement but subsequent movement of the needle retention chamber in a rearward direction is limited to maintain said chamber within the syringe barrel.
In the first embodiment, positive locking structure is fixed within the barrel at a fixed location. The locking structure comprises a constriction of the barrel diameter comprising a first stop while the needle retention chamber has a diametrically enlarged section comprising a second stop wherein the second stop can be forced passed the first stop in a forward direction by pressing on the handle but which resists movement in a rearward direction caused by pulling on the handle. The first embodiment further has a handle portion which is removably attached to the needle retention chamber and separable therefrom by a separation force which is less than the force required to force the second stop past the first stop in a rearward direction. The handle is preferably separable from the needle retention chamber by release of the separating parts without breaking them.
The first embodiment further preferably includes a catch on the front end portion which can be forced forward past the first stop by pressing on the handle before the second stop moves past the first stop. As long as the second stop does not move forward past the first stop, the handle can be withdrawn to fill the syringe. The catch on the front end portion of the needle retention chamber limits the amount of rearward travel of the movable parts to establish the maximum design fill volume of the syringe. The catch comes in contact with the first stop. When the plunger is depressed to make the injection, however, the second stop on the back of the needle retention chamber or some intermediate position on the needle retention chamber moves past the first stop and thereby provides the limiting feature previously described which causes a two part handle to separate when the handle is pulled to the rear. Once the handle is pushed forward with all stops beyond the first stop in the barrel, the syringe can be emptied and the retraction mechanism activated by continued forward movement of the handle.
A second embodiment of the invention has the elongated hollow syringe barrel preferably having a retractable needle retractably mounted in the retraction structure located in the front end of the syringe barrel and biased for retraction in a rearward direction. It has a movable handle in the syringe barrel having a front end portion having a piston in sliding sealed contact with the interior of the barrel, a back end portion having a cap at the back end for applying thumb force to the handle and a needle retention chamber in the front end portion of the handle for receiving the retractable needle. In the second embodiment, the positive locking structure is still located within the syringe barrel. It limits movement of the handle in a rearward direction and prevents its removal from the syringe barrel after one use. However, the locking structure moves relative to the barrel in the second embodiment.
The handle carries the locking structure which is movable in only one direction from a first position near the back of the handle to a second position nearer the front of the handle. The locking structure is adapted to positively engage the syringe barrel and limit movement of the needle retention chamber in a rearward direction after the locking structure is moved forward of the first position. The needle retention chamber is preferably located just forward of the second position of the locking structure. The handle preferably has a plurality of stepped serrations and the positive locking structure is preferably a clip having an inwardly angled tab relative to the stepped serrations which allows the clip to move forwardly on the handle while preventing the clip from moving rearwardly. The clip has at least one outwardly angled point which engages the syringe barrel to prevent withdrawal of the handle. The points simply slide along the surface of the handle because they are angled backwardly but prevent rearward movement which causes the points to dig into the inner surface of the barrel. The clip preferably circumscribes part but not all of the stepped serrations of the back end of the barrel in the form of something slightly more than a half circle shape.
A third embodiment of the invention includes all the other syringe features of the first and second embodiments except for a different positive locking structure. In the third embodiment, the positive locking structure to limit movement of the handle in a rearward direction is located within the syringe barrel in a fixed position relative to the barrel. More particularly, said structure is located inside the open back of the barrel. The structure mounted inside of the open back of the barrel in a fixed position relative to the barrel is preferably a springing clip having one or more forwardly angled points which are protected by a sliding collar carried by the handle from contacting the handle during an initial withdrawal of the handle to draw fluid into the barrel. This allows one withdrawal in the handle in a rearward direction from an initial forward position relative to the barrel without engaging the springing points with the handle. When the plunger is depressed in a forward direction, the sliding collar moves forward out of contact with the points of the springing clip whereupon the springing clip engages the handle to prevent its withdrawal. In the third embodiment, the back end portion of the handle has a plurality of stepped serrations like the second embodiment on which the sliding collar carried by the handle resides. The sliding collar has an angled surface which allows the plunger handle to move rearwardly relative to the collar but the collar has a catch which catches the edge of a stepped serration which causes it to move forward with the handle and away from the springing clip. The springing clips simply ride over the stepped serrations without interference as the handle is being moved forward but as soon as the handle is moved backward, the teeth dig into the handle and stop any rearward movement of the handle. A stop surface on the back of the needle retention chamber can contact the collar and prevent further withdrawal of the handle after the handle is pulled back to the maximum extent. The collar is trapped within the barrel.
Although the invention is most effective when combined with a retractable needle mounted in a retraction structure in the front of the syringe, the invention is primarily concerned with the issue of one use and therefore is applicable to syringes with fixed needles as well as syringes with retractably mounted needles.